     (om/transact! version [] #(update-state % msg) :history)))
 
 (defn empty-query [idx]
-  (index-query idx {:query-grid {:cols [{} {} {}]}
+  (index-query idx {:query-grid {:cols (vec (repeat 3 {:cells []}))}
                     :result {}}))
 
 (defn add-query-msg []

                          {:keys [query-idx col-idx]}]
  (will-mount [_]
    (execute-query! owner (single-item-group-expr item-group)
                    (cell-id query-idx col-idx id)))
  (did-update [_ _ _]
    (when-let [result (:result item-group)]
      (clear-chart (cell-id query-idx col-idx id))

     :dropdown-hover false
     :dropdown-active false})
  (will-mount [_]
    (bus/listen-on owner [:result-loaded query-idx col-idx id]
      #(om/update! term :result (select-keys % [:visit-count-by-study-event]))))
  (will-unmount [_]
    (bus/unlisten-all owner))
